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PubMed2002

Poly(ethylene glycol)-mediated molar mass control of short-chain- and medium-chain-length poly(hydroxyalkanoates) from Pseudomonas oleovorans.

Three strains of Pseudomonas oleovorans, a well known poly(hydroxyalkanoate) (PHA) producer, were tested for the ability to control PHA molar mass and end group structure by addition of poly(ethylene glycol) (PEG) to the fermentation medium. Each strain of P. oleovorans - NRRL B-14682 (B-14682), NRRL B-14683 (B-14683), and NRRL B-778 (B-778) - synthesized a different type of PHA from oleic acid when cultured under identical growth conditions. Strain B-14682 produced poly(3-hydroxybutyrate) (PHB), while B-14683 synthesized a medium-chain-length PHA ( mcl-PHA) with a repeat unit composition ranging from C4 to C14 and some mono-unsaturation in the C14 alkyl side chains. Strain B-778 synthesized a mixture of PHB (95 mol%) and mcl-PHA (5 mol%). The addition of 0.5% (v/v) PEG (M(n) =200 g/mol, PEG-200) to the fermentation broth of strains B-14682 and B-778 resulted in chain termination through esterification at the carboxyl terminus of the PHB with PEG chain segments, thus reducing the molar mass by 54% and 23%, respectively. The molar mass of the mcl-PHA produced by strains B-14683 and B-778 also showed a 34% and 47% reduction in the presence of PEG-200, respectively, but no evidence of esterification was present. PEG-400 (M(n) =400 g/mol) had a reduced effect on PHA molar mass. In fact, the molar masses of the mcl-PHA derived from strain B-14683 and both the PHB and mcl-PHA from B-778 were unchanged by PEG-400. In contrast, the PHB produced by B-14682 showed a 35% reduction in molar mass in the presence of PEG-400.

Alkanes↗
PubMed2006

Poly(ethylene oxide)-modified poly(beta-amino ester) nanoparticles as a pH-sensitive system for tumor-targeted delivery of hydrophobic drugs: part 3. Therapeutic efficacy and safety studies in ovarian cancer xenograft model.

PURPOSE: The objective of this study was to evaluate the anti-tumor efficacy and lack of systemic toxicity of paclitaxel when administered in pH-sensitive poly(ethylene oxide) (PEO)-modified poly(beta-amino ester) (PbAE) nanoparticles in mice bearing human ovarian adenocarcinoma (SKOV-3) xenograft. METHODS: Paclitaxel-encapsulated PEO-modified PbAE (PEO-PbAE) nanoparticles were prepared by the solvent displacement method. PEO-modified poly(epsilon-caprolactone) (PCL) (PEO-PCL) nanoparticles were used as a non pH-responsive control formulation. Efficacy studies were conducted in SKOV-3 tumor-bearing athymic (Nu/Nu) mice at an equivalent paclitaxel dose of 20 mg/kg with the control and nanoparticle formulations. Safety of the drug when administered in the control and nanoparticle formulation was determined from blood cell counts and changes in body weight of the animals. RESULTS: The formulated paclitaxel-containing PEO-PbAE and PEO-PCL nanoparticles had a particle size in the range of 100-200 nm and a surface charge of + 39.0 and - 30.8 mV, respectively. After intravenous administration of paclitaxel in these formulations, the tumor growth was inhibited significantly. Both of the formulated nanoparticles tested have shown improved therapeutic efficacy as compared to the paclitaxel aqueous solution. Additionally, significantly lower toxicity profile of paclitaxel was observed with PEO-modified nanoparticles as compared to the aqueous solution formulation CONCLUSION: PEO-modified PbAE nanoparticles are a unique pH-sensitive drug delivery system that elicits enhanced efficacy and safety profile in solid tumor therapy.

Animals↗
PubMed2005

Morphology and metabolism of Ba-alginate encapsulated hepatocytes with galactosylated poly(allyl amine) and poly(vinyl alcohol) as extracellular matrices.

Lactobionic acid, bearing a beta -galactose group, was coupled with poly(allyl amine) to provide synthetic extracellular matrices together with poly(vinyl alcohol) (PVA). The hepatocytes were encapsulated in Ba-alginate capsules with galactosylated poly(allyl amine) (GA) and PVA as extracellular matrices. From microscopic observation, it was revealed that the microcapsule prepared has a highly porous structure with interconnected pores and pore sizes ranging between 50-150 nm on both the surface and the cross-section. It was found, from the permeability experiment of microcapsules using FITC-dextrans with different molecular weights, that the capsule has a molecular weight cut off (MWCO) of 120 kDa, showing the potential that it can function as an immunoprotecting wall. The hepatocytes, cultured with GA and PVA in the core of the microcapsule, rapidly aggregated within a day, thus resulting in good metabolic functions such as albumin synthesis and ammonia removal.

Albumins↗
PubMed2006

Synthesis and characterization of cholesterol-poly(ethylene glycol)-poly(D,L-lactic acid) copolymers for promoting osteoblast attachment and proliferation.

A novel cholesterol-poly(ethylene glycol)-poly(D,L-lactic acid) copolymer (CPEG-PLA) has been synthesized as a potential surface additive for promoting osteoblast attachment and proliferation. The gel permeation chromatography (GPC) and nuclear magnetic resonance spectroscopy (NMR) results indicated the product had expected structure with low polydispersities in the range of 1.1-1.5. By blending the poly(D,L-lactic acid) (PLA) with CPEG-PLA, the surface of modified PLA membrane was investigated by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle. The results revealed the enrichment of PEG chain on the surface. Osteoblast cell line (MC3T3) was chosen to test the cell behavior on modified PLA membranes. The osteoblast test about cell attachment, proliferation, cell viability and cell morphology investigation on CPEG-PLA modified PLA substrates showed the CPEG-PLA with 15 and 5 ethylene glycol units promoted osteoblast attachment and growth, while the CPEG-PLA with 30 ethylene glycol units prevent osteoblast adhesion and proliferation. This simple surface treatment method may have potentials for tissue engineering and other biomedical applications.

3T3 Cells↗
PubMed2006

Poly(2-hydroxyethyl methacrylate) microspheres/liquid poly(dimethylsiloxane) composition for correction of small defects in face: histological evaluation in animal experiment.

Two kinds of composition based on commercial liquid poly(dimethylsiloxane) and laboratory-made poly(2-hydroxyethyl methacrylate) (PHEMA) microspheres of different size fractions (30-40 or 125-180 microm) were prepared. Tissue reaction on injection of the compositions, optimum microsphere size and morphology were investigated in the experiments on rats. The microspheres induced foreign body reaction characterized by an increased content of fibroblasts and mild infiltration of injection field by inflammatory cells. The 125-180 microm microspheres seemed to be well covered with poly(dimethylsiloxane) and more uniformly distributed in the tissue than the 30-40 microm ones. As a result, the extent of foreign body reaction induced by the former microspheres was somewhat lower than that induced by the latter. Moreover, time-dependent degradation of 30-40 microm PHEMA microspheres was more pronounced than that of 125-180 microm ones, which can affect duration of the aesthetic effect after prospective facioplasty. Results of histological investigations demonstrate a good prospect of the proposed composition for contour and bulk facioplasty of small soft tissue defects and skin wrinkles.

Animals↗
PubMed2005

Poly(ethylene oxide)-modified poly(beta-amino ester) nanoparticles as a pH-sensitive system for tumor-targeted delivery of hydrophobic drugs: part 2. In vivo distribution and tumor localization studies.

PURPOSE: This study was carried out to determine the biodistribution profiles and tumor localization potential of poly(ethylene oxide) (PEO)-modified poly(beta-amino ester) (PbAE) as a novel, pH-sensitive biodegradable polymeric nanoparticulate system for tumor-targeted drug delivery. METHODS: The biodistribution studies of PEO-modified PbAE and PEO-modified poly(epsilon-caprolactone) (PCL), a non-pH-sensitive polymer, nanoparticle systems were carried out in normal mice using 111indium-oxine [111In] as a lipophilic radiolabel encapsulated within the polymeric matrix, and the distribution of the nanoparticles was studied in plasma and all the vital organs following intravenous administration. Solid tumors were developed on nude mice using human ovarian carcinoma xenograft (SKOV-3) and the change in concentrations of tritium [3H]-labeled paclitaxel encapsulated in polymeric nanoparticles was examined in blood, tumor mass, and liver. RESULTS: Study in normal mice with a gamma-emitting isotope [111In] provided a thorough biodistribution analysis of the PEO-modified nanoparticulate carrier systems, whereas 3H-paclitaxel was useful to understand the change in concentration and tumor localization of anticancer compound directly in major sites of distribution. Both PEO-PbAE and PEO-PCL nanoparticles showed long systemic circulating properties by virtue of surface modification with PEO-containing triblock block copolymer (Pluronic stabilizer. Although the PCL nanoparticles showed higher uptake by the reticuloendothelial system, the PbAE nanoparticles effectively delivered the encapsulated payload into the tumor mass. CONCLUSIONS: PEO-modified PbAE nanoparticles showed considerable passive tumor targeting potential in early stages of biodistribution via the enhanced permeation and retention (EPR) mechanism. This prompts a detailed biodistribution profiling of the nanocarrier for prolonged periods to provide conclusive evidence for superiority of the delivery system.

Amino Acids↗
PubMed1996

Preparation and characterization of poly-(D,L-lactide-co-glycolide) and poly-(L-lactic acid) microspheres with entrapped pneumotropic bacterial antigens.

Poly-(lactide-co-glycolide) microspheres with entrapped antigen have shown considerable promise as controlled release vaccines. To enhance the immunomodulatory effect of LW 50020, a bacterial lysate of seven common respiratory pathogens used perorally as an immunomodulator, we prepared poly-(D,L-lactide-co-glycolide) (PLG) and poly-(L-lactic acid) (PLA) microspheres with entrapped immunomodulator by solvent evaporation or solvent extraction double emulsion techniques. Physical properties, such as particle size, LW 50020 entrapment rate, antigen release patterns and morphological characteristics were investigated. All preparations displayed a high degree of antigen loading up to 95%, whereas size, surface morphology and antigen release patterns were significantly influenced by the method of preparation and the polymer components used. Solvent evaporation microspheres are porous particles from 0.8 micron to 2.0 microns in diameter, that show a rapid antigen release for PLG, and a moderate antigen release for PLA microspheres within 33 days. Solvent extraction microspheres have proven to be particles from 1.1 microns to 5.0 microns in diameter showing a smooth surface and a medium antigen release rate over 33 days. SDS-PAGE and immunoblotting of extracted antigen confirmed that the molecular weight and antigenicity of the immunomodulator remained unaltered by the entrapment procedure.

Adjuvants, Immunologic↗
PubMed1981

Aliphatic polyesters II. The degradation of poly (DL-lactide), poly (epsilon-caprolactone), and their copolymers in vivo.

The mechanisms of biodegradation of poly (DL-lactide), poly (epsilon-caprolactone), and copolymers of epsilon-caprolactone with DL-dilactide, delta-valerolactone, and DL-epsilon-decalactone in rabbit were shown to be qualitatively similar. However, the rate of the first stage of the degradation process, non-enzymatic random hydrolytic chain scission, varied by an order of magnitude and was dependent on morphological as well as chemical effects. Weight loss was generally not observed until the molecular weight had decreased to 15,000 or less. Poly (DL-lactide) differed from the other polyesters studied, the rate of chain scission increasing after the commencement of weight loss. The rate of weight loss was greater and the period prior to weight loss was shorter when the comonomer content of copolymers of epsilon-caprolactone was sufficient to reduce the melting point of epsilon-caproate sequences to body temperature.

Animals↗
PubMed1990

XPS and SSIMS analysis of the surface chemical structure of poly(caprolactone) and poly(beta-hydroxybutyrate-beta-hydroxyvalerate) copolymers.

The surface chemical structures of poly(beta-hydroxybutyrate), poly(caprolactone) and poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) have been analysed using static secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The X-ray photoelectron spectroscopy data confirm the purity of the polyester surfaces and there is close agreement between the stoichiometric and experimentally determined ratios of the peaks and different carbon environments within the C1s envelopes. The static secondary ion mass spectrometry analysis reveals general fragmentation pathways which permit the ready distinction between the different polyesters examined. The differentiation of the different monomer repeat units in the copolymer together with the detection of some ions representative of the random copolymer sequence are also possible in the static secondary ion mass spectrometry analysis.

Biocompatible Materials↗
PubMed1986

Degradation of poly(3-hydroxybutyrate) by poly(3-hydroxybutyrate) depolymerase from Alcaligenes faecalis T1.

The extracellular poly(3-hydroxybutyrate) depolymerase purified from Alcaligenes faecalis T1 has two disulfide bonds, one of which appears to be necessary for the full enzyme activity. This depolymerase hydrolyzed not only hydrophobic poly(3-hydroxybutyrate) but also water-soluble trimer and larger oligomers of D-(-)-3-hydroxybutyrate, regardless of their solubilities in water. Kinetic analyses with oligomers of various sizes indicated that the substrate cleaving site of the enzyme consisted of four subsites with individual affinities for monomer units of the substrate. Analyses of the hydrolytic products of oligomers, which had labeled D-(-)-3-hydroxybutyrate at the hydroxy terminus, showed that the enzyme cleaved only the second ester linkage from the hydroxy terminus of the trimer and tetramer, and acted as an endo-type hydrolase toward the pentamer and higher oligomers. The enzyme appeared to have a hydrophobic site which interacted with poly(3-hydroxybutyrate) and determined the affinity of the enzyme toward the hydrophobic substrate.

Alcaligenes↗
PubMed2005

Synthesis and characterization of novel biotinylated biodegradable poly(ethylene glycol)-b-poly(carbonate-lactic acid) copolymers.

Poly(ethylene glycol)-b-poly(5-benzyloxy-trimethylene carbonate-lactic acid) copolymers (PEG-b-P(BTMC-LA)) were synthesized by ring-opening polymerization of lactide and 5-benzyloxy trimethylene carbonate in the presence of mono-hydroxyl poly(ethylene glycol) with diethyl zinc as catalyst. They were further converted into deprotected copolymers with the pendant hydroxyl groups by hydrogenolysis in the presence of Pd(OH)2/C, and finally conjugated with biotin through the free hydroxyl groups. Gel permeation chromatography, Fourier transform infrared, differential scanning calorimetry and 1H nuclear magnetic resonance studies confirmed the copolymer structures and successful attachment of biotin to the copolymer.

Absorbable Implants↗
PubMed2006

Plastic reference electrodes and plastic potentiometric cells with dispersion cast poly(3,4-ethylenedioxythiophene) and poly(vinyl chloride) based membranes.

A simple procedure of preparing low cost, planar and disposable reference electrodes for potentiometric applications is presented. This method is essentially the same as used for obtaining all-plastic ion-selective electrodes and thus promising for simple fabrication of complete cells. Commercially available aqueous dispersion of poly(3,4-ethylenedioxythiophene) doped by poly(4-styrenesulfonate) ions (PEDOT-PSS, Baytron P) is simply cast on a non-conducting plastic support (transparent foil for laser printers). This layer is covered by a non-selective poly(vinyl chloride) based membrane containing solid AgCl and KCl, added to obtain a stable potential. The conducting polymer layer plays a double role, of electrical contact and ion-to-electron transducer, enhancing the potential stability. The reference electrodes obtained exhibit independence of the kind and concentration of electrolyte applied as well as very low sensitivity to interferences: redox reactants and H+ ions; they are also characterized by both potential stability and low polarisability, sufficient for potentiometric applications. Cells of plastic electrodes (indicator and reference ones) are tested using an arrangement with Pb2+ or Ca2+ selective sensors. Potentiometric characteristic of such cells is satisfactory, well comparable with that using a classical electrode arrangement.

Biosensing Techniques↗
PubMed2004

The effect of the processing and formulation parameters on the size of nanoparticles based on block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) with and without hydrolytically sensitive groups.

Block copolymers of poly(ethylene glycol) (PEG) as a hydrophilic block and N-isopropylacrylamide (PNIPAAm) or poly (NIPAAm-co-N-(2-hydroxypropyl) methacrylamide-dilactate) (poly(NIPAAm-co-HPMAm-dilactate)) as a thermosensitive block, are able to self-assemble in water into nanoparticles above the cloud point (CP) of the thermosensitive block. The influence of processing and the formulation parameters on the size of the nanoparticles was studied using dynamic light scattering. PNIPAAm-b-PEG 2000 polymers were not suitable for the formation of small and stable particles. Block copolymers with PEG 5000 and 10000 formed relatively small and stable particles in aqueous solutions at temperatures above the CP of the thermosensitive block. Their size decreased with increasing molecular weight of the thermosensitive block, decreasing polymer concentration and using water instead of phosphate buffered saline as solvent. Extrusion and ultrasonication were inefficient methods to size down the polymeric nanoparticles. The heating rate of the polymer solutions was a dominant factor for the size of the nanoparticles. When an aqueous polymer solution was slowly heated through the CP, rather large particles (> or = 200 nm) were formed. Regardless the polymer composition, small nanoparticles (50-70 nm) with a narrow size distribution were formed, when a small volume of an aqueous polymer solution below the CP was added to a large volume of heated water. In this way the thermosensitive block copolymers rapidly pass their CP ('heat shock' procedure), resulting in small and stable nanoparticles.

Acrylic Resins↗
PubMed2006

Branched polyesters based on poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(d,l-lactide-co-glycolide): effects of polymer structure on cytotoxicity.

Branched polyesters of the general structure poly[vinyl-3-(dialkylamino)alkylcarbamate-co-vinyl acetate-co-vinyl alcohol]-graft-poly(d,l-lactide-co-glycolide) have shown potential for nano- and micro-scale drug delivery systems. For further optimization of this polymer class their cytotoxicity needs to be characterized establishing structure-toxicity relationships. Effects of type and degree of amine substitution as well as molecular weight on cytotoxicity were evaluated in L929 mouse fibroblasts using a MTT assay whereas interactions with cell membranes were quantified by LDH release and caspase (3/7)-activation. Finally, direct cell-polymer contact assays were conducted. Ungrafted amine-modified polymer backbone yielded IC(50) values in the range of 0.05-10mg/ml. Generally higher toxicities were observed with an increasing degree of amine substitution. Amine substituents could be ranked as diethylaminopropylamine (DEAPA)<diethylaminoethylamine (DEAEA)<dimethylaminopropylamine (DMAPA) but the degree of amine substitution was more dominant than the type of amine function. Membrane interactions seem to cause necrotic cell reactions in a dose-dependent manner for highly charged amine-poly(vinyl alcohol) (PVA) backbones. To attenuate cytotoxic effects DEAPA-PVA backbones were grafted with biodegradable PLGA side chains at molecular ratios of 1:10 and 1:20. Cytotoxicity of extracts of these polymers was significantly lower compared to ungrafted polymers possibly caused by shielding of polycationic backbone with hydrophobic PLGA side chains. P(33)-20, a polymer containing a sufficiently high degree of amine substitution could serve as a lead candidate for further investigations. In conclusion, structure-toxicity relationships could be established and shielding the polycationic backbone using PLGA side chains seems to be a promising strategy meriting further investigations.

Animals↗
PubMed2004

UV-induced graft copolymerization of monoacrylate-poly(ethylene glycol) onto poly(3-hydroxyoctanoate) to reduce protein adsorption and platelet adhesion.

Homogeneous solutions of poly(3-hydroxyoctanoate) (PHO) and the monoacrylate-poly(ethylene glycol) (PEGMA) monomer in chloroform were irradiated with UV light to obtain PEGMA-grafted PHO (PEGMA-g-PHO) copolymers. Variables affecting the degree of grafting (DG), such as the time of UV irradiation and the concentrations of the PEGMA monomer and initiator, were investigated. The PEGMA-g-PHO copolymers were characterized by measuring the water contact angle, molecular weight, thermal transition temperatures and mechanical properties, as well as by nuclear magnetic resonance spectroscopy. The results from all of these measurements indicate that PEGMA groups were present on the PHO polymer. The protein adsorption and platelet adhesion on the PEGMA-g-PHO surfaces were examined using poly(L-lactide) (PLLA) surfaces as the control. The proteins and platelets had a significantly lower tendency to adhere to the PEGMA-g-PHO copolymers than to PLLA. The graft copolymer with a high DG of PEGMA was very effective in reducing the protein adsorption and platelet adhesion and did not activate the platelets. The results obtained in this study suggest that PEGMA-g-PHO copolymers have the potential to be used as blood-contacting devices in a broad range of biomedical applications.

Acrylates↗
PubMed2006

Ftorafur loading and controlled release from poly(ethyl-2-cyanoacrylate) and poly(butylcyanoacrylate) nanospheres.

In the present work, a method is described to prepare polymeric colloidal nanospheres, consisting of poly(ethyl-2-cyanoacrylate) (PE-2-CA) or poly(butylcyanoacrylate) (PBCA), loaded with the anticancer drug ftorafur. The method is based on the anionic polymerization procedure, often used in the synthesis of poly(alkylcyanoacrylate) nanospheres for drug delivery. A detailed investigation of the capabilities of both polymeric nanoparticles to load this drug is shown. The effect of synthesis residuals and degradation products on the absorbance of supernatants was considered in the loading and release measurement methodologies, because of their potential perturbing influence on the determination of ftorafur concentration in solution. We found the existence of two mechanisms of drug incorporation: absorption or entrapment in the polymeric network, and surface adsorption, detectable by means of zeta potential and spectrophotometric measurements. Among the factors affecting the drug incorporation to the polymer network, the type of polymer, the pH and the drug concentration are the main determining ones. Moreover, the acidity of the medium needs to be controlled in order to avoid the formation of macroaggregates of solids. The optimum loading conditions were used to perform ftorafur release evaluations from polymeric particles, and the influence of the mechanism of drug incorporation, the amount of drug loaded, and the type of polymer on the drug release were studied.

Absorption↗
PubMed2006

Self-diffusion study of micelles in poly(oxyethylene)-polydimethylsiloxane diblock copolymer and poly(oxyethylene) alkyl ether systems.

Self-diffusion constants of amphiphilic molecules in D(2)O solutions of mixed poly(oxyethylene)-polydimethylsiloxane diblock copolymer (POE-PDMS, Si(m)C(3)EO(n)) and poly(oxyethylene) dodecyl ether (C(12)EO(n)) were measured by pulsed-field-gradient NMR method. In the D(2)O/Si(25)C(3)EO(51.6)/C(12)EO(8) or D(2)O/Si(52)C(3)EO(51.6)/C(12)EO(8) systems, small and large micelles coexist in a wide range of Si(m)C(3)EO(51.6) fraction in total amphiphiles, whereas such a coexisting phenomenon does not take place in the D(2)O/Si(5.8)C(3)EO(51.6)/C(12)EO(8) system. The coexisting phenomenon also takes place in the D(2)O/Si(25)C(3)EO(51.6)/C(12)EO(5) system although the range of mixing fraction is limited. By obtaining each contribution of surfactant and copolymer molecules to the attenuation decay of the echo signal from the proton of the poly(oxyethylene) chain, we could evaluate the composition of the mixed micelles in the D(2)O/Si(25)C(3)EO(51.6)/C(12)EO(8) system. The copolymer content in the mixed micelle increases proportionally to the copolymer mole fraction in the aqueous solution. From the series of self-diffusion measurements, we can conclude that the miscibility of Si(m)C(3)EO(n) and C(12)EO(n) in aqueous micelles becomes poor and the coexisting phenomenon takes place when the PDMS chain becomes much longer than the dodecyl chain of C(12)EO(n) or the POE chain of C(12)EO(n) becomes long. Furthermore it is also revealed that very few silicone copolymer molecules can be incorporated in small surfactant micelles.

Journal Article↗
PubMed2004

Camptothecin derivative-loaded poly(caprolactone-co-lactide)-b-PEG-b-poly(caprolactone-co-lactide) nanoparticles and their biodistribution in mice.

Triblock copolymers of poly(caprolactone-co-lactide)-b-PEG-b-poly(caprolactone-co-lactide) (PCLLA-PEG-PCLLA) were synthesized by ring opening copolymerization of caprolactone and lactide in the presence of poly(ethylene glycol) (PEG). With such triblock copolymers, PCLLA-PEG-PCLLA nanoparticles entrapping 10-hydroxycamptothecin-10,20-diisobutyl dicarbonate (HCPT-1), a derivative of the antitumor drug 10-hydroxycamptothecin (HCPT), were prepared by nano-precipitation method and characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The investigations on drug loading, in vitro release and body distribution in mice after intravenous (i.v.) administration were also carried out. It is found that the obtained nanoparticles showed smooth surface and spherical shape with the controllable size in the range of 70-180 nm, and drug loading content varied from 3.3% to 7.0% depending on the copolymer composition and preparation conditions. The in vitro release behavior exhibited a sustaining release manner and was affected by particle size as well as copolymer composition. The results of body distribution study in mice show that the blood concentration of HCPT-1 could be maintained for a long period and the tissue distribution was influenced by the particle size to some extent. These results suggest that the PCLLA-PEG-PCLLA nanoparticles seem to be a promising delivery system for poorly soluble antitumor drugs or their derivatives.

Animals↗